Double diaphragm shaping of composite materials, assemblies for such shaping, and resulting composite materials

ABSTRACT

Disclosed herein are methods for isolating a composite material from the environment, as well as the isolated composite material. Also disclosed herein are methods for shaping a composite material that include the use of isolated composite materials. For example, disclosed is a method for mechanical thermoforming of a composite material to form a shaped composite material.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a divisional application of U.S. application Ser.No. 16/484,770, filed on Aug. 8, 2019, which is a National Stage Entryof PCT/EP2018/053132, filed on Feb. 8, 2018, which claims priority to GBPatent Application Number 1702071.0, filed on Feb. 8, 2017, and GBPatent Application Number 1716869.1, filed on Oct. 13, 2017. The entirecontents of these applications are incorporated herein by reference.

BACKGROUND

Fiber-reinforced polymer composite materials have gained widespread usein many industries, such as aerospace, automotive, marine, industrial,construction, and a wide variety of consumer products. Compositematerials are often preferred because they are lightweight, but stillexhibit high strength and corrosion resistance, particularly in harshenvironments.

Such fiber-reinforced polymer composite materials are typically madefrom either pre-impregnated materials or from resin infusion processes.Pre-impregnated materials, or “prepregs” are formed of fibresimpregnated with a curable matrix resin, such as epoxy. The resincontent in the prepreg is relatively high, typically 40%-65% by volume.Multiple plies of prepregs may be cut to size for laying up, thensubsequently assembled and shaped in a molding tool. In the case wherethe prepreg cannot be easily adapted to the shape of the molding tool,heating may be applied to the prepregs in order to gradually deform itto the shape of the molding surface. Fiber-reinforced polymer compositematerials may also be made by liquid molding processes that involveresin infusion technologies. These processes include, for example, ResinTransfer Molding (RTM), Liquid Resin Infusion (LRI), Vacuum AssistedResin Transfer Molding (VARTM), Resin Infusion with Flexible Tooling(RIFT), Vacuum Assisted Resin Infusion (VARI), Resin Film Infusion(RFI), Controlled Atmospheric Pressure Resin Infusion (CAPRI), VAP(Vacuum Assisted Process), Single Line Injection (SLI) and ConstantPressure Infusion (CPI). In a resin infusion process, dry binderedfibers are arranged in a mold as a preform, followed by injection orinfusion directly in-situ with liquid matrix resin. After injection orinfusion, the resin-infused preform is cured to provide a finishedcomposite article.

For both types of material, the process for three-dimensional shaping(or molding) of the composite material is critical to the appearance,properties and performance of the final molded product. For example,preforms are often shaped into detailed geometries using a hand layupprocess, which is time consuming and often results in part-to-partvariation. Vacuum forming methods for shaping composite materials alsoexist, where differential pressure is used to aid in the formation of ashaped composite material. See, e.g., U.S. Pat. Nos. 5,578,158 and5,648,109. However, these vacuum forming methods are generally “offline”processes, because vacuum formation is a separate process step from thecuring step. Robots and/or actuators can also be used to manipulatematerials as they enter a tool cavity within a press. Typically, therobot/actuators clamp around the periphery of the materials, and thenmove with the material as the press closes and the materials are drawnin. The aim in such processes is to maintain tension in the X and Y axesto allow for controlled forming of the composite materials. In somecases, shear pins are positioned around the outside of the toolingcavity, such the pins pierce the material that is to be formed. When thetooling is closed, tension in the X and Y axes is maintained as thematerials shear or tear across the pins, but significant excess materialmust be used around the edge of the part. Finally, tooling can includereconfigurable pins that can be individually actuated to a desiredpattern. The actuation of these reconfigurable pins, coupled with avacuum/suction force, deforms the material. See, e.g., U.S. Pat. No.6,484,776.

Each of the processes described above have their own disadvantages andshortcomings: for example, they are often time consuming and/or theproduct is still prone to out of plane wrinkling and otherimperfections. Nor do these processes take into account the rheologicalbehavior and cure characteristics of the composite materials beingshaped. Moreover, the composite materials are generally exposed toenvironmental conditions, which can easily contaminate the final moldedproduct. Finally, there are currently no methods that are capable ofutilizing existing infrastructure and equipment, such as metal stampingor pressing presses, without additional hardware or equipment.

SUMMARY

With a goal of providing an assembly for isolating a composite materialfrom environmental contaminants as well as a molding process that notonly addresses the disadvantages and shortcomings of other methods knownin the art, but also takes into consideration the rheological behaviorand cure characteristics of the composite material and also allows thepotential for using existing infrastructure and equipment, a new methodfor shaping a composite material is disclosed herein.

Accordingly, in one aspect, the present teachings provide methods forisolating a composite material from the environment. Such methodsinclude:

-   -   (a) surrounding a substantially planar composite material with a        gas-impermeable, flexible, frameless diaphragm structure, and    -   (b) creating a sealed pocket in the diaphragm structure, which        houses the composite material alone, by removing air from        between the composite material and the diaphragm structure and        sealing all open edges of the diaphragm structure, such that        contaminants are impeded from entering the sealed pocket without        use of a frame for a period of at least about 1 month under        ambient conditions.

In some embodiments, creating a sealed pocket comprises sealing all openedges of a diaphragm bag or folded diaphragm sheet disposed about thecomposite material. In other embodiments, creating a sealed pocketcomprises sealing two diaphragm sheets around the entire periphery ofthe composite material.

In some embodiments, sealing all open edges of the diaphragm structurecomprises mechanical sealing, application of adhesive, heat sealing,welding or any combination thereof.

In some embodiments, removing air comprises applying vacuum pressurebetween the composite material and the flexible diaphragm structure.

In some embodiments, the diaphragm structure comprises a film comprisingone or more layers, each independently selected from a plastic layer oran elastic layer. The film can be disposable or reusable.

In some embodiments, sealing the diaphragm structure provides a sealstrength sufficient to inhibit intake of contaminants during subsequentshaping of the composite material. In some embodiments, sealing thediaphragm structure provides a seal strength sufficient to inhibitintake of contaminants during shipping and handling of the compositematerial. In certain embodiments, contaminants are impeded from enteringthe sealed pocket without use of a frame for a period of up to about 6months under ambient conditions.

In some embodiments, the sealed pocket maintains vacuum integrity for aperiod of at least about 1 month under ambient conditions.

In another aspect, the present teachings provide methods for shaping acomposite material. Such methods include:

-   -   (a) surrounding a substantially planar composite material with a        gas-impermeable, flexible, frameless diaphragm structure;    -   (b) creating a sealed pocket in the diaphragm structure, which        houses the composite material alone, by removing air from        between the composite material and the diaphragm structure and        sealing all open edges of the diaphragm structure, thereby        forming a layered structure, such that: air and contaminants are        impeded from entering the sealed pocket without use of a frame,        and the composite material is held stationary within the sealed        pocket until heat, force, or a combination thereof, is applied        thereto;    -   (c) optionally disposing the diaphragm structure within a        structural frame; and    -   (d) shaping the composite material within the sealed pocket of        the diaphragm structure.

In some embodiments, creating a sealed pocket comprises sealing all openedges of a diaphragm bag or folded diaphragm sheet disposed about thecomposite material. In other embodiments, creating a sealed pocketcomprises sealing two diaphragm sheets around the entire periphery ofthe composite material.

In some embodiments, sealing all open edges of the diaphragm structurecomprises mechanical sealing, application of adhesive, heat sealing,welding or any combination thereof.

In some embodiments, removing air comprises applying vacuum pressurebetween the composite material and the flexible diaphragm structure.

In some embodiments, the diaphragm structure comprises a film comprisingone or more layers, each independently selected from a plastic layer oran elastic layer. The film can be disposable or reusable.

In some embodiments, sealing the diaphragm structure provides a sealstrength sufficient to inhibit intake of contaminants for a period oftime from 1 month to 6 months under ambient conditions. In otherembodiments, sealing the diaphragm structure provides a seal strengthsufficient to inhibit intake of contaminants during the shaping in step(c). In still other embodiments, sealing the diaphragm structureprovides a seal strength sufficient to inhibit intake of contaminantsduring shipping and handling of the composite material. In furtherembodiments, sealing the diaphragm structure provides a seal strengthsufficient to inhibit intake of contaminants during storage of thecomposite material, wherein storage occurs for up to about 6 months.

In some embodiments, the sealed pocket maintains vacuum integrity for aperiod of at least about 1 month under ambient conditions.

In some embodiments, the method further comprises machining thecomposite material according to a pattern prior to step (a).

In some embodiments, the layered structure is manipulated by automatedmeans.

In still another aspect, the present teachings provide a method forshaping a composite material. Such method generally includes:

-   -   (a) placing a substantially planar composite material between an        upper flexible diaphragm and a lower flexible diaphragm by        creating a sealed pocket between the diaphragms which houses the        composite material,    -   (b) bringing the upper flexible diaphragm and the lower flexible        diaphragm into intimate contact with the composite material,        thereby forming a layered structure, wherein the composite        material is held stationary between the upper flexible diaphragm        and the lower flexible diaphragm until heat or force is applied        to the layered structure;    -   (c) optionally pre-heating the layered structure in a heating        apparatus at a temperature sufficient to either lower the        viscosity of the composite material or soften the diaphragms;    -   (d) positioning the layered structure in a press tool comprising        a male mold and a corresponding female mold separated by a gap,        wherein the male mold and the female mold each independently        have a non-planar molding surface,    -   (e) compressing the layered structure between the male mold and        the female mold by closing the gap between the male mold and the        female mold; and    -   (f) maintaining the male mold and the female mold in a closed        position until the viscosity of the layered structure reaches a        level sufficient to maintain a molded shape.

In some embodiments, the composite material can be machined according toa pattern prior to step (a).

In some embodiments, step (e) comprises partially closing the gapbetween the male mold and the female mold such that a smaller gap isformed between the molds, which smaller gap is subsequently closed aftera specific time or viscosity is reached. In some embodiments, step (e)comprises closing the gap between the male mold and the female mold at aspeed of between about 0.7 mm/s and about 400 mm/s, while maintainingthe male mold and the female mold at a temperature above the softeningpoint of the composite material. In certain embodiments, step (e) iscarried out until the viscosity of the composite material is less than1.0×10⁸ mPa.

In some embodiments, the male mold and the female mold are maintained ata temperature above ambient temperature. For example, in someembodiments, the male mold and the female mold are maintained at atemperature above 100° C. In some embodiments, the male mold and femalemold are maintained in a closed position for between about 10 secondsand about 30 minutes.

In some embodiments, step (b) comprises applying a vacuum pressure of atleast about 670 mbar between the upper flexible diaphragm and the lowerflexible diaphragm.

In some embodiments, the method also includes (g) cooling the layeredstructure on the tool to a temperature that is below the softeningtemperature of the composite material. In other embodiments, the methodalso includes (g) removing the layered structure from the tool while thelayered structure is above the softening temperature of the compositematerial.

In some embodiments, the upper diaphragm and the lower diaphragm areheld together by a structural frame comprising a top frame, a centerframe and a bottom frame, wherein:

the lower diaphragm is held between the bottom frame and the centerframe; and the upper diaphragm is held between the center frame and thetop frame.

The center frame can be configured to supply a source of vacuum to theassembly. In other embodiments, the upper diaphragm and the lowerdiaphragm are held together by a structural frame comprising a top frameand a bottom frame, wherein both the lower diaphragm and the upperdiaphragm are held between the center frame and the top frame.

The material used to make the upper and lower diaphragms are generallyselected based on their desired function, as described in more detailbelow. In some embodiments, the upper diaphragm and the lower diaphragmare each independently selected from a film comprising one or morelayers, each independently selected from a rubber layer, a siliconelayer and a plastic layer.

The heating apparatus may be any apparatus known in the art, and in someembodiments may be particularly selected from a contact heater or an IRheater. In some embodiments, the layered structure is positioned in thepress tool and/or in the optional heating apparatus by automated means.

In some embodiments, no vacuum pressure is applied to any portion of thepress tool.

In yet another aspect, the present teachings provide isolated compositematerials. Such materials include a substantially planar compositematerial sealed within an air-evacuated pocket of a gas-impermeable,flexible, frameless diaphragm structure, wherein contaminants areimpeded from entering the air-evacuated pocket for a period of at leastabout 1 month under ambient conditions.

In some embodiments, contaminants are impeded from entering theair-evacuated pocket during shaping of the composite material. In otherembodiments, contaminants are impeded from entering the air-evacuatedpocket during storage, shipping and/or handling of the compositematerial. In still other embodiments, contaminants are impeded fromentering the air-evacuated pocket during storage of the compositematerial, wherein storage occurs for up to about 6 months.

In some embodiments, the air-evacuated pocket maintains vacuum integrityfor a period of at least about 1 month under ambient conditions.

Composite materials for use in connection with the present teachingsinclude structural fibers. Such structural fibers include, but are notlimited to, aramid, high-modulus polyethylene (PE), polyester,poly-p-phenylene-benzobisoxazole (PBO), carbon, glass, quartz, alumina,zirconia, silicon carbide, basalt, natural fibers and combinationsthereof. Composite materials for use in connection with the presentteachings also include a binder or matrix material. Such binder ormatrix material includes, but is not limited to thermoplastic polymers,thermoset resins, and combinations thereof.

BRIEF DESCRIPTION OF THE DRAWINGS

FIGS. 1A and 1B illustrate the formation of an exemplary framed layeredstructure in accordance with the present teachings.

FIGS. 2A and 2B illustrate the formation of an exemplary framelesslayered structure in accordance with the present teachings.

FIGS. 3A and 3B illustrate an exemplary molding process (using a framedlayered structure) in accordance with the present teachings.

DETAILED DESCRIPTION

In view of the potential drawbacks of composite material processing,including processing time, part-to-part variation and productcontamination, there still exists a need to develop faster, improved andmore reliable assemblies and processes. It is also desirable to takerheological behavior and cure characteristics into account and, ifpossible, to provide a process which can take full advantage of existingequipment (e.g., metal stamps or presses). The present disclosureprovides assemblies for isolating a composite material fromenvironmental contaminants, including frameless assemblies which aresuitable for storage, handling and/or transport as well as methods forshaping composite materials, including methods using a double-diaphragmmechanical thermoforming process, which—both individually andcollectively—address these drawbacks.

Isolated Composite Materials

Traditional metal sheets are typically formed, e.g., into shapedproducts such as automotive panels, using drawing and/or stampingtechniques. Because the metal is quite impervious to atmosphericinfluences, such as oxygen, dust and oil from the machinery, the metalcan be formed into highly complex and intricate shapes without the needfor isolation from such atmospheric influences in order to avoid defectsduring shaping. Unfortunately, the same is not typically true ofcomposite materials. Using traditional metal stamping equipment directlyon composite materials would typically result in an imperfect, unevensurface which is unacceptable in consumer products, such as automobiles.Therefore, in certain aspects, the present invention is directed to anassembly for use in the shaping of composite materials. Such assembliesisolate the composite materials, e.g., so that they can be shaped onexisting metal-stamping equipment.

In some aspects, therefore, the present teachings provide methods offorming an assembly for use in shaping a composite material. Suchmethods, which can isolate a composite material from the environment,include:

-   -   (a) placing a substantially planar composite material between an        upper flexible diaphragm and a lower flexible diaphragm by        creating a pocket between the diaphragms which houses the        composite material, and    -   (b) bringing the upper flexible diaphragm and the lower flexible        diaphragm into intimate contact with the composite material,        thereby forming a layered structure, wherein the composite        material is held stationary between the upper flexible diaphragm        and the lower flexible diaphragm until heat or force is applied        to the layered structure.

As used herein, the term “substantially planar” refers to a materialthat has one plane that is measurably larger than the other two planes(for example, at least 2, 3, 4 or 5 times larger, or more). In someembodiments, the substantially planar material has thickness variationalong the largest plane. For example, the composite material may includereinforcement materials such as pad-ups (i.e., localized increases inthe quantity of plies) or ply drops (i.e., localized decreases in thequantity of plies), material changes, and/or areas where the compositetransitions, e.g., to fabric. In other embodiments, the substantiallyplanar material exhibits minimal thickness variation along the area ofthe composite material. For example, the term substantially planar canmean that the composite material has a global thickness variation of nogreater than +/−15% over 90% of the area. In some embodiments, thethickness variation is no greater than +/−10% over 90% of the area.Substantially planar is not intended to denote a perfectly flatmaterial, but also includes materials that have slight variations inconcavity and/or convexity. As used herein, the term “flexible” refersto a material capable of deformation without significant return forces.Flexible materials typically have a flexibility factor (the product ofthe Young's modulus measured in Pascals and the overall thicknessmeasured in meters) of between about 1,000 N/m and about 2,500,000 N/m,for example between about 1,500 N/m and about 2,000,000 N/m, or betweenabout 2,000 N/m and about 1,500,000 N/m.

In certain embodiments, the pocket housing the composite material isdefined by a structural frame which houses the composite material heldbetween the diaphragms. Referring now to FIG. 1A, in certainembodiments, the substantially planar composite material (110) is placedbetween an upper flexible diaphragm (120) and a lower flexible diaphragm(130). This creates a pocket (140) between the diaphragms which housesthe composite material. In certain embodiments, this pocket would bedefined by a structural frame which houses the composite material heldbetween the diaphragms. For example, the lower flexible diaphragm can beplaced onto a bed (150) which holds a bottom frame (160); the compositematerial (110) can be subsequently laid on top of the lower flexiblediaphragm (120); a central frame (170) can then be placed on the lowerdiaphragm, followed by the upper flexible diaphragm (130) and finally atop frame (180). In some embodiments, the central frame may be excluded.The top, central (where present) and bottom frames maintain the desireddiaphragm shape through a supported perimeter, e.g., by the positioningof clamps at predetermined intervals around the perimeter. Such top,central and bottom frames can be manufactured based on the size andshape of the composite material to be molded. Optionally,pre-manufactured structural support frames are known in the art for usewith conventional metal or composite press tools (e.g., frommanufacturers such as Langzauner or Schubert). In some embodiments thecentral frame (170) may include a means for removing air, for example avacuum inlet or other valve. The vacuum inlet, if present, is connectedto a vacuum source (e.g. a vacuum pump). In some embodiments, the pocketthat houses the composite may be a sealed pocket, e.g., an airtightsealed pocket, whereby the structural frame is disposed about the entireperiphery of the composite material.

Referring now to FIG. 1B, the upper flexible diaphragm (130) and thelower flexible diaphragm (120) are brought into intimate contact (see190 and exploded view thereof) with the composite material (110), toform a layered structure. This may be accomplished for example byapplying vacuum pressure between the upper flexible diaphragm and lowerflexible diaphragm. In other embodiments, this may be accomplished byphysically applying pressure (e.g., by hand or by mechanical means) onthe upper and/or lower flexible diaphragm(s) to remove air. Vacuumpressure may be desired in certain cases, e.g., to extract residual airwhich may hinder molding performance, to hinder deformation or wrinklingof the composite material (or its components), to aid in maintainingfiber alignment, to provide support to the materials during the processand during shaping, and/or to maintain desired thickness at elevatedtemperatures. The term “vacuum pressure” as used herein refers to vacuumpressures of less than 1 atmosphere (or less than 1013 mbar). In someembodiments, the vacuum pressure between the diaphragms is set to lessthan about 1 atmosphere, less than about 800 mbar, less than about 700mbar, or less than about 600 mbar. In some embodiments, the vacuumpressure between the diaphragms is set to about 670 mbar. At this point,whether by vacuum or by mechanical means, the composite material isfirmly held between the diaphragms, such that it is stationary until theapplication of heat or force. Such stationary layered structure can beadvantageous, for example, because the composite material held withinthe layered structure is not only maintained stationary in its locationwith sufficient tension across its X and Y axes, but it is also indexed.That is to say, the composite material may be placed (e.g., by automatedmeans) in a specific position between the diaphragms within thestationary layered structure.

This indexed stationary layered structure may then be placed (e.g., byautomated means) in a specific position in the press tool (as describedin more detail hereinbelow), such that the press tool consistentlyengages a predetermined area of the composite material. A stationarylayered structure may, therefore, be reliably used to produce multiplecopies of a molded product without the need to index each compositematerial blank individually.

In some circumstances, manufacturing a framed assembly at a locationother than the location of the shaping equipment could presentsignificant, potentially insurmountable, difficulties. Weight, size andother aspects of the assembly have a tremendous effect on the ability tostore and/or transport an isolated composite material. It is, therefore,advantageous or even necessary to have a frameless assembly in certaincircumstances. Therefore, in some embodiments, the pocket housing thecomposite material is defined by the diaphragm structure itself and thepresent teachings provide a frameless assembly for use in shaping acomposite material. Methods for isolating a composite material from theenvironment using a frameless assembly include:

-   -   (a) surrounding a substantially planar composite material with a        gas-impermeable, flexible, frameless diaphragm structure, and    -   (b) creating a sealed pocket in the diaphragm structure, which        houses the composite material alone, by removing air from        between the composite material and the diaphragm structure and        sealing all open edges of the diaphragm structure, such that        contaminants are impeded from entering the sealed pocket without        use of a frame.

Referring now to FIG. 2 , in certain embodiments the substantiallyplanar composite material (210) is surrounded by a gas-impermeableflexible diaphragm structure. The diaphragm structure can be, forexample, a bag comprising one or more open edges (220) or one or moresheets of material that are disposed about the composite material. Forexample, the composite material can be placed in between two sheets(230). This creates a pocket (240) within the bag or between the sheetswhich houses the composite material. Air is then removed from betweenthe composite material and the diaphragm structure. This can beaccomplished by applying vacuum pressure between the composite materialand the diaphragm structure, by physically applying pressure (e.g., byhand or by mechanical means) to the outer surface of the diaphragmstructure, or by some combination thereof. As with the framed assembly,in a frameless assembly, a particular vacuum pressure may be selected,e.g., to also hinder deformation or wrinkling of the composite material(or its components), to aid in maintaining fiber alignment, to providesupport to the materials during the process and during shaping, and/orto maintain desired thickness at elevated temperatures. In someembodiments, the vacuum pressure between the diaphragm structure and thecomposite material is set to less than about 1 atmosphere, less thanabout 800 mbar, less than about 700 mbar (e.g., about 670 mbar), or lessthan about 600 mbar. The diaphragm structure is then sealed (260) toform a sealed pocket within the diaphragm structure which houses thecomposite material within a layered structure (250), such thatcontaminants are impeded from entering the sealed pocket without use ofa frame. As used herein, the term “contaminants” refers to air,particulates, oil, and any other contaminant that could substantiallyaffect the surface properties or mechanical properties of the compositematerial. In some embodiments, the air is removed and the open edges aresealed in a single step. For example, air can be removed and edges maybe sealed at the same time using mechanical pressure. In otherembodiments, the air is removed and the open edges are sealed indiscrete steps. For example, air can be removed using a vacuum, followedby sealing using mechanical or other means.

In some embodiments, contaminants are impeded from entering the sealedpocket without use of a frame for a period of at least about 1 monthunder ambient conditions. In certain embodiments, contaminants areimpeded from entering the sealed pocket without use of a frame for aperiod of at least about 2, 3, 4 or even 5 months under ambientconditions. In some embodiments, contaminants are impeded from enteringthe sealed pocket without use of a frame for a period of up to about 6months under ambient conditions; however in certain embodiments,contaminants may be impeded from entering the sealed pocket without useof a frame for a period of greater than 6 months under ambientconditions. In certain embodiments, contaminants are impeded fromentering the sealed pocket without use of a frame for a period of atleast about 2 months under low temperature conditions, i.e., −18° C. orless. In certain embodiments, contaminants are impeded from entering thesealed pocket without use of a frame for a period of at least about 4,6, 8, 10 or even 12 months under low temperature conditions.

The materials and methods used to create a sealed pocket will depend onthe nature and shape of the diaphragm material used in the diaphragmstructure. For example, if the diaphragm structure is a bag, creating asealed pocket refers to placing the composite material in the interiorof the bag and sealing the open edge of the bag. If the diaphragmstructure is a folded sheet, creating a sealed pocket refers to sealingthe three open edges of the folded sheet, with the composite materialbeing disposed within the fold of the sheet. If, on the other hand, thediaphragm structure is two diaphragm sheets, creating a sealed pocketrefers to sealing the four open edges of the two diaphragm sheets, withthe composite material disposed between the two sheets (i.e., sealingaround the entire periphery of the composite material). In all cases,each open edge may be sealed in a straight line, or in any non-linearmanner.

Additionally, a number of methods for sealing the diaphragm materials(in the absence of a structural frame) can be utilized. For example, theopen edges of the diaphragm structure can be mechanically sealed. Inother embodiments, the open edges of the diaphragm structure can besealed using adhesive. In other embodiments, the open edges of thediaphragm structure can be welded. In still other embodiments, the openedges of the diaphragm structure can be sealed using heat.

Sealing the composite material in the pocket of the diaphragm structurenot only impedes contaminants under static, ambient conditions, but alsocan impede contaminants under dynamic circumstances. In someembodiments, sealing the diaphragm structure provides a seal strengthsufficient to inhibit intake of contaminants during subsequent shapingof the composite material. In some embodiments, sealing the diaphragmstructure provides a seal strength sufficient to inhibit intake ofcontaminants during storage, shipping and/or handling of the compositematerial.

A frameless assembly capable of impeding contaminants can also becapable of maintaining a vacuum. Therefore, at this point—and similar toa framed assembly—the composite material is firmly held within thesealed pocket, and can be held stationary until the application of heator force. In particular, in some embodiments, the sealed pocketmaintains vacuum integrity for a period of at least about 1 month underambient conditions. In certain embodiments, the sealed pocket maintainsvacuum integrity for a period of at least about 2, 3, 4, 5 or 6 months,or more, under ambient conditions. As used herein, the term “vacuumintegrity” refers to the ability of the frameless assembly tosubstantially retain negative pressure within the sealed pocket. Whenthe sealed pocket maintains vacuum integrity, the composite material ismaintained stationary in its location within the frameless assembly,with sufficient tension across its X and Y axes, and is also indexed(i.e., in a specific position within the frameless assembly). In someembodiments, this indexed frameless assembly can have the sameadvantages as the stationary layered structure defined in the context ofa framed assembly. In other words, the indexed frameless assembly may beplaced in a specific position in the press tool, such that the presstool consistently engages a predetermined area of the compositematerial. In some embodiments, however, the frameless assembly will bedisposed within a structural frame prior to shaping the compositematerial. The use of an indexed frameless assembly would also providesignificant advantages when used with a structural frame, not only interms of the storage and shipping capabilities discussed in detailabove, but also during shaping. In particular, the indexed framelessassembly may be reliably used—without the need for additionalindexing—with a structural frame, even after storage, handling, and/orshipping.

Diaphragm Materials and Diaphragm Structures

As used herein, the term “diaphragm” refers to any barrier that dividesor separates two distinct physical areas. The term “diaphragm structure”refers to an assembly of one or more diaphragms that define an exteriorspace and an isolated interior space, e.g., the area within a sealedpocket and the area outside of the sealed pocket. The diaphragms areflexible and may be either elastic or non-elastically deformable sheetsof material. Typically, diaphragm thickness ranges between about 10microns and about 200 microns, for example, between about 20 microns andabout 150 microns. Particularly advantageous diaphragms have a thicknessof between about 30 microns and about 100 microns. In some embodiments,the material used to make the diaphragms is not particularly limited andcan be, for example, rubbers, silicones, plastics, thermoplastics, orsimilar materials. In certain embodiments, however, the material used tomake the diaphragms includes a film comprising one or more layers, eachindependently selected from a plastic layer or an elastic layer. Thediaphragms may be comprised of a single material or may include multiplematerials, e.g., arranged in layers. The upper diaphragm and the lowerdiaphragm of a diaphragm structure, for example, can each independentlybe selected from a film comprising one or more layers, each individuallayer being the same as or different than the other layers in thediaphragm. Diaphragm material can be formed into a film usingconventional casting or extrusion procedures. In some embodiments, thefilm is disposable. In other embodiments, the film is reusable.

The diaphragm material can also be chosen to have a number ofproperties, depending upon the desired function. For example, in someembodiments, the diaphragm is self-releasing. That is, the diaphragm caneasily release from the final molded part and/or the molded assembly caneasily release from the tooling. In other embodiments, the diaphragm isdesigned to temporarily (or lightly) adhere to the molded compositematerial. Such temporary adhesion may be advantageous to protect thefinal molded part, e.g., during subsequent processing, transport and/orstorage. In still other embodiments, the diaphragm is designed topermanently adhere to the molded composite material. Such temporaryadhesion may be advantageous to provide a permanent protective coatingand/or paint coating to the final molded part. The diaphragm materialmay be chosen based on its specific physical properties. For example, insome embodiments, the material used to make the diaphragms has anelongation to failure of above 100%. In some embodiments, the materialused to make the diaphragms has a melting temperature that is similar to(e.g., within 10° C. of) the molding temperature of the compositematerial.

In some embodiments, the diaphragms are permeable to air. In otherembodiments, the diaphragms are impermeable to air, such that togetherthey are able to form a sealed pocket. The sealed pocket impedescontaminants (e.g., air, particulates, oil, etc.) from entering thesealed pocket for a period of time. In some embodiments, the impermeablediaphragms form an airtight sealed pocket. As used herein, the term“airtight” refers to the ability of a material to hold a vacuum for theduration of the tooling process. This airtight sealed pocket isadvantageous, for example, when a vacuum is used to place the upper andlower diaphragms in intimate contact with the composite material.

Composite Materials

As used herein, the term “composite material” refers to an assembly ofstructural fibers and a binder or matrix material. Structural fibers maybe organic fibers, inorganic fibers or mixtures thereof, including forexample commercially available structural fibers such as carbon fibers,glass fibers, aramid fibers (e.g., Kevlar), high-modulus polyethylene(PE) fibers, polyester fibers, poly-p-phenylene-benzobisoxazole (PBO)fibers, quartz fibers, alumina fibers, zirconia fibers, silicon carbidefibers, other ceramic fibers, basalt, natural fibers and mixturesthereof. It is noted that end uses that require high-strength compositestructures would typically employ fibers having a high tensile strength(e.g., ≥3500 MPa or ≥500 ksi). Such structural fibers may include one ormultiple layers of fibrous material in any conventional configuration,including for example, unidirectional tape (uni-tape) webs, non-wovenmats or veils, woven fabrics, knitted fabrics, non-crimped fabrics,fiber tows and combinations thereof. It is to be understood thatstructural fibers may be included as one or multiple plies across all ora portion of the composite material, or in the form of pad-ups or plydrops, with localised increases/decreases in thickness.

The fibrous material is held in place and stabilized by a binder ormatrix material, such that alignment of the fibrous material ismaintained and the stabilized material can stored, transported andhandled (e.g., shaped or otherwise deformed) without fraying,unraveling, pulling apart, buckling, wrinkling or otherwise reducing theintegrity of the fibrous material. Fibrous materials held by a smallamount of binder (e.g., typically less than about 10% by weight) aretypically referred to as fibrous preforms. Such preforms would besuitable for resin infusion applications, such as RTM. Fibrous materialsmay also be held by larger amounts of matrix materials (generally called“prepregs” when referring to fibers impregnated with a matrix), andwould thus be suitable for final product formation without furtheraddition of resin.

The binder or matrix material is generally selected from thermoplasticpolymers, thermoset resins, and combinations thereof. When used to forma preform, such thermoplastic polymers and thermoset resins may beintroduced in various forms, such as powder, spray, liquid, paste, film,fibers, and non-woven veils. Means for utilizing these various forms aregenerally known in the art.

Thermoplastic materials include, for example, polyesters, polyamides,polyimides, polycarbonates, poly(methyl methacrylates), polyaromatics,polyesteramides, polyamideimides, polyetherimides, polyaramides,polyarylates, polyaryletherketones, polyetheretherketones,polyetherketoneketones, polyacrylates, poly(ester) carbonates,poly(methyl methacrylates/butyl acrylates), polysulphones,polyarylsulphones, copolymers thereof and combinations thereof. In someembodiments, the thermoplastic material may also include one or morereactive end groups, such as amine or hydroxyl groups, which arereactive to epoxides or curing agents.

Thermoset materials include, for example, epoxy resins, bismaleimideresins, formaldehyde-condensate resins (including formaldehyde-phenolresins), cyanate resins, isocyanate resins, phenolic resins and mixturesthereof. The epoxy resin may be mono or poly-glycidyl derivative of oneor more compounds selected from the group consisting of aromaticdiamines, aromatic monoprimary amines, aminophenols, polyhydric phenols,polyhydric alcohols, and polycarboxylic acids. The epoxy resins may alsobe multifunctional (e.g., di-functional, tri-functional, andtetra-functional epoxies).

In some embodiments, a combination of thermoplastic polymer(s) andthermoset resin(s) are used in the composite material. For example,certain combinations may operate with synergistic effect concerning flowcontrol and flexibility. In such combinations, the thermoplasticpolymers would provide flow control and flexibility to the blend,dominating the typically low viscosity, brittle thermoset resins.

Double Diaphragm Processes for Shaping Composite Material

The present teachings also include methods for shaping compositematerials using the assemblies provided herein. In some embodiments, themethods include the use of a framed assembly and in other embodiments,the methods include the use of a frameless assembly. In still otherembodiments, the methods can use either a framed or a framelessassembly.

In some aspects, therefore, the present teachings provide methods forshaping a composite material that generally include:

-   -   (a) surrounding a substantially planar composite material with a        gas-impermeable, flexible, frameless diaphragm structure;    -   (b) creating a sealed pocket in the diaphragm structure, which        houses the composite material alone, by removing air from        between the composite material and the diaphragm structure and        sealing all open edges of the diaphragm structure, thereby        forming a layered structure, such that:

contaminants are impeded from entering the sealed pocket without use ofa frame, and the composite material is held stationary within the sealedpocket until heat, force or a combination thereof is applied thereto;

-   -   (c) optionally disposing the diaphragm structure within a        structural frame; and    -   (d) shaping the composite material within the sealed pocket of        the frameless diaphragm structure.

Shaping the composite material in step (d) can include vacuumthermoforming, mechanical thermoforming, or a combination thereof.

Vacuum thermoforming generally includes

(a″) positioning the layered structure over a housing with a moldpositioned therein, the mold having a non-planar molding surface, so asto define a sealed chamber bounded by the diaphragm structure and thehousing, and such that the lower diaphragm is positioned above themolding surface;

(b″) optionally heating the layered structure at a temperaturesufficient to either lower the viscosity of the composite materialand/or soften the diaphragm structure

(c″) creating a vacuum inside the sealed chamber between the diaphragmstructure and the housing by removing air, whereby the layered structureis pulled toward the molding surface and eventually conforms thereto,

(d″) maintaining the vacuum until the viscosity of the layered structurereaches a level sufficient for the composite material to maintain amolded shape

General parameters known in the art for vacuum thermoforming can beused. For example, in some embodiments, air is removed in step (c″) at arate of 1 mbar/15 mins or faster until a vacuum pressure of 950 mbar orbelow is reached. In other embodiments, heating is maintained while airis removed in step (c″).

In some embodiments, the vacuum thermoforming further includes coolingthe layered structure on the mold to a temperature that is below thesoftening temperature of the composite material. In yet otherembodiments, the vacuum thermoforming further includes (e″) removing thelayered structure from the tool while the layered structure is above thesoftening temperature of the composite material.

Mechanical thermoforming, on the other hand, can include

(a′) optionally pre-heating the layered structure in a heating apparatusat a temperature sufficient to lower the viscosity of the compositematerial, to soften the diaphragm structure, or both;

(b′) positioning the layered structure in a press tool comprising a malemold and a corresponding female mold separated by a gap, wherein themale mold and the female mold each independently have a non-planarmolding surface,

(c′) compressing the layered structure between the male mold and thefemale mold by closing the gap between the male mold and the femalemold; and

(d′) maintaining the male mold and the female mold in a closed positionuntil the viscosity of the layered structure reaches a level sufficientfor the composite material to maintain a molded shape.

It is particularly noted that the mechanical thermoforming methodsdescribed above can be used in combination with either a framed assemblyor a frameless assembly. For example, in some embodiments, the presentteachings provide methods for shaping a composite material thatgenerally include:

(a°) optionally pre-heating a layered structure, the layered structurecomprising a composite material disposed within a diaphragm structure,in a heating apparatus at a temperature sufficient to either lower theviscosity of the composite material or soften the diaphragms;

(b°) positioning the layered structure in a press tool comprising a malemold and a corresponding female mold separated by a gap, wherein themale mold and the female mold each independently have a non-planarmolding surface,

(c°) compressing the layered structure between the male mold and thefemale mold by closing the gap between the male mold and the femalemold; and

(d°) maintaining the male mold and the female mold in a closed positionuntil the viscosity of the layered structure reaches a level sufficientto maintain a molded shape.

In still other embodiments, the present teachings provide methods forshaping a composite material that generally include:

-   -   (a) placing a substantially planar composite material between an        upper flexible diaphragm and a lower flexible diaphragm by        creating a sealed pocket between the diaphragms which houses the        composite material,    -   (b) bringing the upper flexible diaphragm and the lower flexible        diaphragm into intimate contact with the composite material,        thereby forming a layered structure, wherein the composite        material is held stationary between the upper flexible diaphragm        and the lower flexible diaphragm until heat or force is applied        to the layered structure;    -   (c) optionally pre-heating the layered structure in a heating        apparatus at a temperature sufficient to either lower the        viscosity of the composite material or soften the diaphragms;    -   (d) positioning the layered structure in a press tool comprising        a male mold and a corresponding female mold separated by a gap,        wherein the male mold and the female mold each independently        have a non-planar molding surface,    -   (e) compressing the layered structure between the male mold and        the female mold by closing the gap between the male mold and the        female mold; and    -   (f) maintaining the male mold and the female mold in a closed        position until the viscosity of the layered structure reaches a        level sufficient to maintain a molded shape.

Referring now to FIG. 3A, the layered structure (310) may, in somecases, be pre-heated in a heating apparatus (320). The layered structurecan be placed in the heating apparatus manually or by automated means,e.g., using an automated shuttle (325). This heating apparatus can beany heater that can be used in the formation or molding of metal orcomposite material products, for example, a contact heater or aninfrared (IR) heater. In some cases this pre-heating softens the upperflexible diaphragm and the lower flexible diaphragm, e.g., so that theyare more pliable during formation of the final molded product. In somecases, this pre-heating brings the composite material held within thelayered structure to a desired viscosity or temperature. Pre-heating mayoccur in a heating apparatus heated to a temperature of above about 75°C., 100° C., 125° C., 150° C., 175° C., 200° C. or even higher. Thistemperature can be adjusted, for example, depending upon the identity ofthe diaphragms and/or components in the composite material. Suchpre-heating is advantageous, for example, if it is desired to minimizeor eliminate heating of the press tool and/or to minimize the amount oftime that the layered structure resides within the press tool.

In order to form the final molded product, the layered structure ispositioned in a press tool. In some embodiments, no vacuum pressure isapplied to any portion of the press tool. In other embodiments,localized vacuum is applied to the tool surface, for example to removeentrapped air between the layered structure and the tool. In suchembodiments, however, the vacuum is typically not used as a force toform the shape of the final molded product. The layered structure can beplaced in the press tool manually or by automated means, e.g., using anautomated shuttle (325). This press tool generally includes a male mold(330) and a female mold (340), which are separated by a gap (350). Eachmold has a non-planar molding surface (360 and 370, respectively). Themolding surfaces are fixed, i.e., not reconfigurable. The moldingsurfaces are also typically matched, i.e., the male mold correspondingapproximately to the opposite of the female mold; and in someembodiments may be perfectly matched. However, in some embodiments, themale and female molds are such that, when closed, the thickness betweenthem varies. In certain embodiments, the layered structure is positionedin the gap at a specific, predetermined distance between the male moldand the female mold. Referring to FIG. 2B, the layered structure is thencompressed between the male mold and the female mold, by closing the gap(380). In some embodiments, this is accomplished by partially closingthe gap between the male mold and the female mold to form a smaller gapbetween the molds. This smaller gap is subsequently closed after aspecific time or viscosity is reached. It is understood that “closingthe gap” refers to compressing the molds such that a pre-determinedfinal cavity thickness along the Z axis (390) is obtained between them.Final cavity thickness can be adjusted, e.g., by controlling where themolds stop in relation to each other, and the choice of thickness can bemade by the operator of the molds and will depend on the nature of thefinal molded product. In some embodiments, the final cavity thickness issubstantially uniform, i.e., the process produces a two-sided moldedfinal product with a thickness that varies by less than 5%. In someembodiments, the process produces a final molded product with athickness that varies by less than about 4%, e.g., less than about 3%,less than about 2% or even less than about 1%. In other embodiments, themale and female tools may be configured to provide a cavity thicknessthat purposely varies across the X and Y axes.

In certain embodiments, the male mold and the female mold are maintainedat a temperature above ambient temperature. For example, they may bemaintained at a temperature of above about 75° C., 100° C., 125° C.,150° C., 175° C., 200° C. or even higher. This temperature can beadjusted depending upon the identity (and the viscosity) of thecomponents in the composite material. The molds, for example, can bemaintained at a temperature above the softening point of the binder ormatrix material used in the composite material. In some embodiments, thecomposite material comprises a thermoset material and molds aremaintained at temperatures between about 100° C. and 200° C. In otherembodiments, composite material comprises a thermoplastic material andthe molds are maintained at temperatures above about 200° C. Typically,the layered structure will be heated at some point, for example duringthe pre-heating step or during the molding process in the press tool orboth, to enable softening of the composite material. The binder ormatrix material in the composite material is in a solid phase at ambienttemperature (20° C.-25° C.), but will soften upon heating. Thissoftening allows molding of the composite material in the press tool.

In some embodiments, the male mold and the female mold are maintained ina closed position for a predetermined time. For example, in someembodiments, the molds are heated and maintained in a closed positionuntil a desired viscosity or temperature is reached. In someembodiments, the molds are maintained in a closed position until theviscosity of the composite material is less than about 1.0×10⁸ mPa. Insome embodiments, the molds are heated and maintained in a closedposition until the binder or matrix material begins to cross-link. Inother embodiments, the molds are not heated, but are maintained in aclosed position fora period of time sufficient for the material tomaintain a molded shape. Molds may be maintained in a closed position,e.g., for between about 5 seconds and about 60 minutes, for example, forbetween about 10 seconds and about 30 minutes or between about 15seconds and about 15 minutes. The length of time that the molds aremaintained in a closed position will depend upon a number of factors,including the identity of the composite material and the temperature ofthe molds.

In certain embodiments, the male mold is driven through the layeredstructure, while the female mold remains static. In other embodiments,the female mold does not remain static, but moves at a rate that isslower than the male mold (such that the male mold still actspredominantly as the forming surface). In still other embodiments, bothmolds move at approximately the same rate of speed to close the gapbetween the molds. The molds are driven at a rate and to a finalpressure sufficient to deform/mold the composite material. For example,the molds may be driven at a rate of between about 0.4 mm/s and about500 mm/s, e.g., between about 0.7 mm/s and about 400 mm/s, e.g., betweenabout 10 mm/s and about 350 mm/s or between about 50 mm/s and 300 mm/s.Additionally, the molds may be driven to a final pressure of betweenabout 100 psi and about 1000 psi, e.g., between about 250 psi and about750 psi. In some embodiments, the molds are driven at a rate and to afinal pressure that have been selected to control the thickness of thefinal molded product while avoiding the formation of wrinkles and thedistortion of structural fibers. In addition, the molds may be driven ata rate and to a final pressure that have been selected to allow therapid formation of final molded parts.

The layered structure is then cooled to below the softening temperatureof the binder or matrix material. This can occur while the layeredstructure remains on the press tool, or after the layered structure isremoved from the press tool. At this point, the binder or matrixmaterial returns to a solid phase and the composite material retains itsnewly formed geometry. If the composite material is a preform, suchpreform will hold its desired shape for subsequent resin infusion.

The present method can reduce the requirement of post-cure machining toachieve the final geometry of structural parts. This post-cureprocessing is not only time-consuming, but also very risky because curedstructural parts cannot be re-shaped. Therefore, damage incurred duringpost-cure processing can result in the part being scrapped. Thus, insome embodiments, the present process includes the step of machining thecomposite material prior to placing it between the upper and lowerdiaphragms. This allows for automated, efficient and easy machining ofthe composite material, instead of a complex process of programming,positioning, and cutting of a cured three-dimensional compositematerial.

The double-diaphragm arrangement described above not only aids in themolding of composite materials, e.g., by maintaining the compositematerial in a stationary position with sufficient tension across its Xand Y axes, but also provides significant additional functionaladvantages. For example, the arrangement protects the composite materialblank from environmental contaminants, such as impurities in the air oron the tooling machinery. This protection enables the (otherwiseunmanageable) use of conventional press tools that are capable ofsignificantly more complex three dimensional geometries than eithervacuum formation or reconfigurable tool technologies. Furthermore, theuse of the double-diaphragm arrangement can allow the mold releaseprocess to be eliminated from the total process. Moreover, it provides afinal molded product that can, if desired, maintain the diaphragm layer,either temporarily or permanently. For example, a temporary layer may bedesired, e.g., for a release coating, whereas a permanent coating may bedesired, e.g., for corona treatment or bonding of the diaphragm materialto the molded part. The function the diaphragms will depend on thediaphragm material used, discussed in more detail below. The doublediaphragm mechanical thermoforming process described herein, therefore,provides an effective and efficient means for producing complexthree-dimensional composite structures in an automated fashion.Three-dimensional composite structures can be produced quickly,repeatedly and on a large-scale. For example, three-dimensionalcomposite structures can be formed from substantially planar compositematerial blanks in 1-10 minute cycles. Such quick, repeatable processesare suitable for the manufacture of automotive parts and paneling, suchas hoods, trunks, door panels, fenders and wheel wells.

EXAMPLES

The following examples are for illustration purposes only, and are notto be construed as limiting the scope of the appended claims.

Example 1: Double Diaphragm Mechanical Thermoforming, Framed

A lower flexible diaphragm made of a plastic film (Solvay, formerlyCytec Industries, EMX045) was vacuumed onto a bed holding a bottomframe. A composite material blank made of a carbon-fiber reinforcedepoxy (Solvay, formerly Cytec Industries, MTM710-1) was laid on top ofthe lower flexible diaphragm, followed by center frame having a vacuuminlet. An upper flexible diaphragm made of the same film as the lowerflexible diaphragm was then placed such that it covered the center frameand composite material blank. The top, center and bottom frames wereclamped together, thereby creating a vacuum tight seal and a sealedpocket bounded by the lower flexible diaphragm, the upper flexiblediaphragm and the center frame. A vacuum was then applied to remove airfrom between the upper flexible diaphragm and the lower flexiblediaphragm, until the vacuum pressure reached 670 mbar. At that point,the composite material blank was firmly supported by both diaphragms,creating a stationary layered structure.

The layered structure was then shuttled into a contact heatingapparatus, where it was heated to 120° C. Once the layered structuretemperature reached 120° C., it was shuttled into a press toolcomprising a matched male mold and female mold, configured in the shapeof a structural automotive door component. The male mold was then driventoward the female mold at a rate of approximately 200 mm/s. The femalemold remained stationary, and both molds were held at 140° C. untilcross linking had begun. The shaped structure was removed from the presstool while still hot and allowed to cool after removal.

The process for shaping the composite material blank was 10 minutes fromstart to finish (i.e., first placement of the lower flexible diaphragmto establishment of final shape).

Example 2: Frameless Isolation of Composite Material

A flat composite material blank made of a carbon-fiber reinforced epoxy(Solvay, formerly Cytec Industries, Solvalite™ 710-1) was disposedbetween two sheets of an 80 micron plastic film (Solvay, formerly CytecIndustries, EMX045). After removing air from between the sheets ofplastic film, the sheets was sealed together at around 140° C., with atotal heat up and cool down duration of approximately 8 seconds. Oncecooled below 80° C., the layered structure formed by the two sheetsdisposed about the composite material blank was found to have adequatestrength and sufficient weld characteristics. The sealed flat blankswere stored for 4 days at 21° C. and 6 months at −18° C., in each casewith no observed intrusion of contaminants.

The same process was done using flat composite material blank made of acarbon-fiber reinforced ester (Solvay, formerly Cytec Industries,Solvalite^(™) 730). The sealed flat blank was stored in a stack at 21°C. for 18 months with no observed intrusion of contaminants.

Prospective Example 3: Double Diaphragm Mechanical Thermoforming usingFrameless Blank

The sealed flat blanks prepared in accordance with Example 2 whichinclude Solvalite™ 710-1, after storage, will be placed within astructural frame, such that the frame is disposed around the peripheryof the composite material blank and the composite material blank isfirmly supported by both sheets of film and the frame. This structurewill then be shuttled into a contact heating apparatus, where it will beheated to 120° C. Once the layered structure temperature reaches 120°C., it will be shuttled into a press tool comprising a matched male moldand female mold, configured in a desired three dimensional shape. Themale mold will then be driven toward the female mold at a rate ofapproximately 200 mm/s. The female mold will remain stationary, and bothmolds will be held at 140° C. until cross linking begins. The shapedstructure will be removed from the press tool while still hot and willbe allowed to cool after removal.

It is anticipated that the process for shaping the composite materialblank will be significantly less than 10 minutes from start to finish(i.e., placement of the sealed flat blank into the frame toestablishment of final shape).

The invention claimed is:
 1. A method for isolating a composite materialfrom the environment, the method comprising: (a) surrounding asubstantially planar composite material with a gas-impermeable,flexible, frameless diaphragm structure, and (b) creating a sealedpocket in the diaphragm structure, which houses the composite materialalone, by removing air from between the composite material and thediaphragm structure and sealing all open edges of the diaphragmstructure, such that contaminants are impeded from entering the sealedpocket without use of a frame for a period of at least about 1 monthunder ambient conditions.
 2. The method of claim 1, wherein creating asealed pocket comprises sealing all open edges of a diaphragm bag orfolded diaphragm sheet, disposed about the composite material.
 3. Themethod of claim 1, wherein creating a sealed pocket, comprises sealingtwo diaphragm sheets around the entire periphery of the compositematerial.
 4. The method of claim 1, wherein sealing all open edges ofthe diaphragm structure comprises mechanical sealing, application ofadhesive, heat sealing, welding or any combination thereof.
 5. Themethod of claim 1, wherein removing air comprises applying vacuumpressure between the composite material and the flexible diaphragmstructure.
 6. The method of claim 1, wherein the diaphragm structurecomprises a film comprising one or more layers, each independentlyselected from a plastic layer or an elastic layer.
 7. The method ofclaim 6, wherein the film is disposable.
 8. The method of claim 6,wherein the film is reusable.
 9. The method of claim 1, wherein sealingthe diaphragm structure provides a seal strength sufficient to inhibitintake of contaminants during subsequent shaping of the compositematerial.
 10. The method of claim 1, wherein sealing the diaphragmstructure provides a seal strength sufficient to inhibit intake ofcontaminants during shipping and handling of the composite material. 11.The method of claim 1, wherein contaminants are impeded from enteringthe sealed pocket without use of a frame for a period of up to about 6months under ambient conditions.
 12. The method of claim 1, wherein thesealed pocket maintains vacuum integrity for a period of at least about1 month under ambient conditions.